The objective of this project is to determine if changes in the mechanisms for control of protein accumulation occur during the aging process. Pulse-chase experiments will be performed to measure in vivo rates of synthesis and degradation of total proteins (protein turnover) in free-living nematodes (Turbatrix aceti) as a function of age. Immunological techniques will also be employed to determine synthetic and degradative rates of individual enzymes known to undergo age-related modifications in T. aceti, including enolase, isocitrate lyase, and phosphoglycerate kinase. The work will be extended to determine if changes in protein turnover occur with age in Fischer 344 rats. Double-isotope and immunological procedures will be used to examine rates of synthesis and degradation of protein in selected tissues, and of specific proteins in these tissues, throughout the lifespan of the animal. The relationship of altered turnover rates (if found) to the appearance of altered enzymes in old organisms will be explored. The results will establish whether or not a failure in the capability of the cell to metabolize defective enzymes occurs with advancing age. The deterioration of such a metabolic system may be an important factor in cellular aging.